Inside the gearcase is what is called the carrier, or the differential. One of the carrier’s jobs is to transfer the engine’s power to the wheels via the gearset and axles. Most important, the carrier allows the left and right wheels to travel at different speeds when turning, in wet conditions, or burnouts. Not all differentials are created equal, that is why Currie and Eaton Detroit have different speeds when touring several different styles of differentials to choose from. From left to right, clutch-type Posi, Detroit locker, Spool, and Truetrac.